وَلَمَّا سُقِطَ فِيٓ أَيۡدِيهِمۡ وَرَأَوۡاْ أَنَّهُمۡ قَدۡ ضَلُّواْ قَالُواْ لَئِن لَّمۡ يَرۡحَمۡنَا رَبُّنَا وَيَغۡفِرۡ لَنَا لَنَكُونَنَّ مِنَ ٱلۡخَٰسِرِينَ ١٤٩
And when regret overcame them1 and they saw that they had gone astray, they said, "If our Lord does not have mercy upon us and forgive us, we will surely be among the losers."
Translation: Saheeh International (English)
1 Literally, "When their hands had been descended upon," i.e., bitten by them out of severe regret.
Each word's meaning and sound
When they regretted their actions and did not know how to make-up for their wrongdoing, realising that they had gone astray from the straight path by worshipping the calf besides to Allah, they said: 'If our Lord does not have mercy on us, by enabling us to do as He instructed, and if He does not forgive us for having worshipped the calf, then we would certainly be among the losers in the life of this world and in the Afterlife.'
Al-Mukhtasar in interpreting the Noble Quran